A lot of mobile equipment, such as mobile phones, organizers or cameras, is provided with several communication channels. A first radio communication channel enables equipment to exchange data with access terminals to distributed networks such as the telephone network or Internet. Access to these networks is controlled by a number of telephone operators which users can subscribe to. This first communication channel provides mobile equipment with the option of communicating easily and quickly with other equipment located a significant distance away. On the other hand, the radio bandwidth is not favorable to the transmission of large volumes of data. The user finds, for example, that the transmission of image files by this channel requires relatively long communication times. Thus, given the subscription rates, the transmission of image files becomes expensive.
A second radio or infrared communication channel can be used locally for data exchanges between devices that are geographically near and share the same communication protocol (Bluetooth, Wi-Fi). The field of coverage of this communication channel has a range limited from 20 to 100 meters. The limited range of the communications however is compensated for by a broad bandwidth and almost free exchanges. The bandwidth from about some hundreds of kbps to some dozens of Mbps enables the transmission of large volumes of data in very short times. The arrival of the Ultra Wide Band (UWB) standard will further increase this bandwidth for short-range transfers.
When the density of the mobile communication equipment in a geographic zone is high, information can flow by multiple hops between equipment from the source equipment towards the target equipment. Various information paths or routes can be proposed in certain cases.
On the contrary, in the absence of any equipment that can act as relay in a given zone, the information to transmit is stored in a memory of the source equipment or the intermediate equipment having the information, until the time when equipment capable of continuing the information transmission is identified. Thus the information flows not only by hops between equipment, but also by using the physical movement of the users of the mobile equipment.
The state of the art is illustrated by documents (1) to (7), whose full references are given at the end of the present description.